Law & Order 10 p.m., Channel 7
If you are 18, you are younger than this series, which premiered in 1990 and finishes up its 19th season tonight. The cast has changed completely over the years, with S. Epatha Merkerson taking the prize as the senior cast member. She started her run as Lieutenant Anita Van Buren in 1993. The show will be back next season, when it will match "Gunsmoke" as the longest-running primetime drama.
The Late Show With David Letterman 11:35 p.m., Channel 4
Yeah, he's still on. All the Conan hubbub can't quite negate that fact. And as time passes, it will be fascinating to see if Dave will benefit from the changes at NBC. Tonight, his guest is Steve Earle, who has a new album of songs by his late friend Townes Van Zandt. Earle is special to fans of "The Wire": He played Bubbles's 12-step sponsor, Walon, and sang the theme song in the final season.
Tattoo Highway 10 p.m., A&E
Epidermis Underpass.
The Cougar 10 p.m., TV Land
The cub scout ends.
Time Warp 8 p.m., Discovery Channel
A giant yo-yo. Try rocking that baby.
Wipeout 8 p.m., Channel 5
Logrolling in our time.
Your Worst Animal Nightmares 9 p.m., Animal Planet
Generally involve rats.
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